Chordoma
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: Notochordoma; chordocarcinoma; chordoepithelioma
Overview
Chordomas are uncommon malignant tumors that account for 1% of intracranial tumors and 4% of all primary bone tumors. They originate from embryonic remnants of the primitive notochord (earliest fetal axial skeleton, extending from the Rathke's pouch to the coccyx). Since chordomas arise in bone, they are usually extradural and result in local bone destruction. They are locally aggressive, but uncommonly metastasise.
Pathophysiology
- Fluid and gelatinous mucoid substance (associated with recent and old haemorrhage) and necrotic areas are found within the tumor.
- In some patients, calcification and sequestered bone fragments are found as well.
- The variety of these components may explain the signal heterogeneity observed on MRI.
- Incomplete delineation of the tumor and microscopic distal extension of tumor cells may explain the frequency of recurrences.
- Physaliphorous cells are classically seen on microscopy.
- Metastatic spread of chordomas is observed in 7-14% of patients and includes nodal, pulmonary, bone, cerebral or abdominal visceral involvement, predominantly from massive tumors.
- True malignant forms of chordomas occasionally have areas of typical chordoma and undifferentiated areas, most often suggestive of fibrosarcoma.
Location
Chordomas are found along the axial skeleton and a relatively evenly distributed among three locations: Sacrococcygeal: 30-50% Spheno-occipital: 30-35% Vertebral body: 15-30%
Sacrococcygeal
This is the most common location, accounting for approximately 30-50% of all chordomas and involving particularly the fourth and fifth sacral segments. In this location a male predilection has been reported (M:F ratio of 2:1) and the tumor may be particularly large at presentation. Chordoma is the most common primary malignant sacral tumor.
Spheno-occipital
The clival region is the next most common, accounting for 30-35% 2-3 of cases. Typically the mass projects in the midline posteriorly indenting the pons. This characteristic appearance has been termed the 'thumb sign". In contrast to sacrococcygeal tumours, there is currently no recognised gender difference.
Vertebral bodies
Chordomas of the vertebral bodies are rare but after lymphoproliferative tumours are nonetheless the most common primary malignancy of the spine in adults. They most commonly involve the cervical spine (particularly C2), followed by the lumbar spine then the thoracic spine. They often extend across the intervertebral disc space, involving more than one vertebral segment. They may extend into the epidural space, compressing the spinal cord, or along the nerve roots, enlarging the neural exit foramen.
Differential Diagnosis
For clival/spheno-occipitial lesions differentials to consider include: Chondrosarcoma of skull base Plasmacytoma Meningioma of skull base Pituitary macroadenoma Ecchordosis physaliphora
For vertebral lesions, consider: Chondrosarcoma ◦neural arch > vertebral body Thoracic spine is the most commonly involved spinal region Chondroid matrix (rings & arcs) Similar MRI appearance to chordomas (low to intermediate signal intensity on T1, hyperintense on T2, enhances)
- Giant cell tumour
- F>M
- Location: sacrum > thoracic spine > cervical spine > lumbar spine
- No mineralised matrix
- Heterogeneous intermediate to hyperintense T2 signal
- Spinal metastases
- Hypointense on T1; variably hyperintense on T2
- Often multiple, involving vertebral bodies and posterior elements
- Plasmacytoma
- Destructive vertebral body lesion (similar appearance to lytic metastases)
Spinal lymphoma
- Multifocal disease
- Heterogenous T2 signal
Epidemiology
- Chordomas occur at any age but are usually seen in adults (30-70 years).
- Those located in the spheno-occipital region most commonly occur in patients 20-40 years of age, whereas sacrococcygeal chordomas are typically seen in a slightly older age group (peak around 50 years).
- They are commonly found in Caucasians.
Prognosis
Prognosis is typically poor, due to the locally aggressive nature of these tumors, with the 10-year survival approximately 40%.
Diagnosis
CT
CT centrally located well-circumscribed destructive lytic lesion, sometimes with marginal sclerosis expansile soft-tissue mass (usually hyper-attenuating relative to the adjacent brain; however, inhomogenous areas may be seen due to cystic necrosis or haemorrhage; the soft-tissue mass is often disproportionately large relative to the bony destruction) irregular intratumoral calcifications (thought to represent sequestra of normal bone rather than dystrophic calcifications) moderate to marked enhancement
MRI
T1: Intermediate to low signal intensity small foci of hyperintensity (intratumoral haemorrhage or a mucus pool)
T2: most exhibit very high signal T1 C+ (Gd): heterogeneous enhancement with a honeycomb appearance corresponding to low T1 signal areas within the tumour GE (gradient echo): confirms haemorrhage if present with blooming.
Treatment
- Traditionally surgical resection has been the first line of treatment in feasible scenarios, with radiotherapy offered for recurrent cases.
- Some advocate the combination of radiation therapy and complete or subtotal surgical resection for selected patients.
- Percutaneous radiofrequency ablation has been trialled as an adjunct.
- Recurrence, including seeding along the operative tract, is common.